compact object

(compact star)

(dense astronomical body such as white dwarf or denser)

A compact object (or compact star) is a collective term for
white dwarves, neutron stars, black holes and other
hypothesized exotic dense stars, which often are stellar remnants,
what's left after a star's fusion has run out.
The term degenerate star is also used for compact objects that
are not black holes.
A compact object merger
is a merger of two such stars, the source of hypothesized detectable
gravitational waves and a luminosity potentially 1015 that of the Sun.